It is well known that hypertoxic cyanides exist in liquid waste from existing production processes of ore dressing, metallurgy, coking and electroplating etc. and methods universally adopted for removing cyanide such as ionic exchange, ozonization or direct electrolytic oxidation are not efficient. For example, in electrolytic oxidiation the current efficiency is not stable, therefore harmful gases are generated in the process and the processing cost is high. During the operation of the niobium anode cyanide processor, explosive gases such as hydrogen and chloramine as well as toxic gases such a nitrogen trichloride, cyanhydrin and chloride acid escaped may cause secondary pollution. In alkaline chlorine process, a chloric oxidant (chlorine, liquid chlorine sodium subchlorate, or bleaching power etc.) is added to the cyanide containing water so as to oxidize and decompose cyanides under alkaline condition. Since availibe chlorine may degrade during the storage of chloric oxidants, it reacts chemically with cyanic ions in the process, generating harmful gases such as cyanic acid and cyanogen chloride. In addition, chloric oxidants are easy to leak out during the transportation, therefore, secondary pollution might be caused. The chlorinecyanogen equivalent weight is not easy to control in the process, which may produce excessive chlorine or cause the cyanogen content to exceed discharge standard. Meanwhile the cost is high.
Ionic exchange is usually used in the desalination of drinking water, and the processing of heavy metal ions and radioactive elements. It is effective in processing liquid waste containing less than 50 PPM of cyanogen and not suitable to process liquid waste containing more than 200 PPM of cyanogen.